The goal of high availability computer network environments is to provide users and other entities with “always on” service. That is, high availability computer network environments should provide reliable, continuous operation service. To accomplish this, network devices in a high availability environment perform error detection and implement recoverability for detected errors. Unfortunately, network devices occasionally fail.
When a network device fails, all network traffic flowing through the failed network device may cease. For an enterprise that depends on such network traffic, this may be unacceptable, even if this failure occurs only for a short time. To minimize the possibility of a failure causing all network traffic to cease, redundant hardware such as a backup controller or a separate backup network device may be installed. When the primary controller fails, this primary controller (which may also be referred to as a “master controller”) may switch over (or, in other words, fail-over) to the backup controller. Likewise, when the primary network device fails, this primary network device (which may also be referred to as a “master network device”) may switch over (or, in other words, fail-over) to the backup network device. After failing over or switching over to the backup device, the backup device becomes the master device. High availability clusters often include such primary and backup network devices.
Typically, a server provider may deploy a backup network device adjacent to a customer or subscriber premises to ensure high availability for those customers or subscribers that access the service provider via the master network device. The service provider may then ensure fail-over of all sessions routed through the master network device to the backup network device so as to provide high availability for those customers or subscribers that access the service provider network via the master network device.